This invention relates, generally, to high speed sheet feeder machines, also known as inserters. More particularly, it relates to an apparatus that prevents over-rotation of a pusher apparatus for an inserter when operated at very high speeds.
High speed inserters have pusher members that follow a predetermined path of travel in the form of a loop that lies in a vertical plane so that they can reciprocate without stopping and without having abrupt changes in direction. The pushers push sheets into envelopes when said pushers are in a forward position at the lower elevation of the loop. They retreat along the higher elevation of the loop to a rearward position after each insertion and then travel forwardly again to the forward position and the cycle endlessly repeats for as long as the machine is in operation. Some high speed machines can insert ten thousand sheets per hour into envelopes, but that speed seems to be an upper limit. At such high speeds, the momentum of the pushers causes the respective leading ends or heads of the pushers to swing out of their normal path of travel in a rearward bight region of the loop where the rearward-to-forward change in direction occurs. Once out of position, they lose their operability and the machine has to be shut down to re-position the pusher members.
The respective trailing ends of the pusher members are rotatably mounted on a transversely disposed rod that follows the loop-shaped path of travel. If the rod is well oiled and the friction between the trailing end of each pusher member and the rod is very low, the pusher member will not usually rotate out of its operable position at speeds below ten thousand insertions per hour. However, the friction between the rod and the trailing end gradually increases as the machine operates, with the result that pusher member rotation eventually occurs. At speeds above ten thousand insertions per hour, the pusher members rotate out of position even when the rod is well-oiled.
It should be understood that each transversely disposed rod typically carries three pushers in equidistantly, laterally spaced relation to one another. Moreover, there may be three or four transverse rods per machine, equidistantly and longitudinally spaced apart from one another along the extent of the loop-shaped path of travel.
The obvious solution to the problem is to run the machines at a speed that does not cause the pusher members to depart from their normal path, and to frequently oil the rod that carries the trailing end of the pusher members. That is not an acceptable solution, however, when there is a demand for insertions in excess of ten thousand per hour and where time requirements do not allow for frequent shut-downs for oiling.
In view of the prior art in at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how a pusher assembly could be built that could operate at speeds in excess of twelve thousand insertions per hour.
The longstanding but heretofore unfulfilled need for an inserter machine capable of operating at speeds in excess of ten thousand sheet insertions per hour is now met by a new, useful, and nonobvious apparatus for enabling high speed travel of a pusher apparatus. A groove that follows a loop-shaped path of travel is formed in opposing, transversely spaced apart vertical walls of the push member assembly. A transversely disposed rod extends between the opposing vertical walls and the trailing end of each pusher is rotatably mounted thereto but the opposing ends of the transversely disposed rod do not directly engage the opposing grooves. Instead, a pair of carriage members rotatably engage the transversely disposed rod at its opposite ends, there being one carriage member at each end of the transversely disposed rod. Each carriage member has a truncate longitudinal extent and has a transversely offset roller rotatably mounted at its leading end. The roller is disposed in and travels about its associated groove. The longitudinally extending part of the carriage rotatably engages the transversely disposed rod. The transversely disposed rod is connected at its opposite ends to chains that define the loop-shaped path of travel of the pushers.
An upstanding stop member is formed in the trailing end of the carriage member.
A stationary flat barrier plate is mounted to the trailing end of each side wall of the pusher assembly. Accordingly, each flat barrier plate is disposed just rearwardly (a sixteenth of an inch or so) of the rearward bight region of the loop-shaped path of travel. The stop member at the trailing end of each carriage slidingly abuts the flat barrier plate as the carriage negotiates the bight region at the rearward end of the loop-shaped path of travel, and such abutment prevents rotation of said at least one pusher, relative to the transversely disposed rod upon which it is mounted, even at speeds in excess of ten thousand insertions per hour.
The primary object of this invention is to provide an improved pusher apparatus that enables a high speed sheet feeder to operate at speeds in excess of ten thousand insertions per hour.
A more specific object is to accomplish the foregoing object by means of an apparatus that can be retrofit onto existing machines.
These and other important objects, advantages, and features of the invention will become clear as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims.